Vibrating flowmeters or conduit sensors, such as Coriolis mass flowmeters and vibrating densitometers, typically operate by detecting motion of a vibrating conduit that contains a flowing material. Properties associated with the material in the conduit, such as mass flow, density and the like, can be determined by processing measurement signals received from motion transducers associated with the conduit. The vibration modes of the vibrating material-filled system generally are affected by the combined mass, stiffness, and damping characteristics of the conduit and the material contained therein.
Material flows into the flow meter from a connected pipeline on the inlet side of the vibrating meter. The material is then directed through the fluid tube or fluid tubes and exits the flow meter to a pipeline connected on the outlet side.
A driver, such as a voice-coil style driver, applies a force to the one or more fluid tubes. The force causes the one or more fluid tubes to oscillate. When there is no material flowing through the flow meter, all points along a fluid tube oscillate with an identical phase. As a material begins to flow through the fluid tubes, Coriolis accelerations cause each point along the fluid tubes to have a different phase with respect to other points along the fluid tubes. The phase on the inlet side of the fluid tube lags the driver, while the phase on the outlet side leads the driver. Sensors are placed at two different points on the fluid tube to produce sinusoidal signals representative of the motion of the fluid tube at the two points. A phase difference of the two signals received from the sensors is calculated in units of time.
The phase difference between the two sensor signals is proportional to the mass flow rate of the material flowing through the fluid tube or fluid tubes. The mass flow rate of the material is determined by multiplying the phase difference by a flow calibration factor. The flow calibration factor is dependent upon material properties and cross sectional properties of the fluid tube. One of the major characteristics of the fluid tube that affects the flow calibration factor is the fluid tube's stiffness. Prior to installation of the flow meter into a pipeline, the flow calibration factor is determined by a calibration process. In the calibration process, a fluid is passed through the fluid tube at a given flow rate and the proportion between the phase difference and the flow rate is calculated. The fluid tube's stiffness and damping characteristics are also determined during the calibration process as is generally known in the art.
One advantage of a Coriolis flow meter is that the accuracy of the measured mass flow rate is not affected by wear of moving components in the flow meter, as there are no moving components in the vibrating fluid tube. The flow rate is determined by multiplying the phase difference between two points on the fluid tube and the flow calibration factor. The only input is the sinusoidal signals from the sensors indicating the oscillation of two points on the fluid tube. The phase difference is calculated from the sinusoidal signals. Since the flow calibration factor is proportional to the material and cross sectional properties of the fluid tube, the phase difference measurement and the flow calibration factor are not affected by wear of moving components in the flow meter.
A typical Coriolis mass flowmeter includes one or more transducers (or pickoff sensors), which are typically employed in order to measure a vibrational response of the flow conduit or conduits, and are typically located at positions upstream and downstream of the actuator. The pickoff sensors are connected to electronic instrumentation. The instrumentation receives signals from the two pickoff sensors and processes the signals in order to derive a mass flow rate measurement, among other things.
Typical Coriolis flow meters measure flow and/or density through the use of a coil and magnet as a pickoff sensor to measure the motion of a meter's vibrating flow tube/tubes. The mass flow rate through the meter is determined from the phase difference between multiple pickoff signals located near the inlet and outlet of the meter's flow tubes. However, it is possible to measure flow using strain gages in place of coil/magnet sensors. A fundamental difference between the two sensor types is that coil/magnet sensors measure the velocity of the flow tubes and strain gages measure the strain of the flow tubes.
Typically manifolds provide the inlet and outlet path for material entry and exit through the flow tubes, and these are generally coupled to flanges that attach to exterior conduits. The manifolds are coupled to the flow tubes and also case portions. In many situations, a portion of the fluid tubes extend out of the case and are joined to a pipeline interface, such as a manifold. The fluid tubes are generally joined to the manifold by welding.
Flow meters also are utilized in specialized applications, for example, high pressure, cryogenic and hygienic systems. Cleaning-In-Place (CIP) and Sterilization-In-Place (SIP) systems are systems designed for automatic cleaning and disinfecting without major disassembly and assembly work. The cleaning can be carried out with automated or manual systems and is a reliable and repeatable process that meets the stringent hygiene regulations demanded by the food, dairy, biotechnology and pharmaceutical industries. CIP and SIP is critical to many industries including food, dairy, beverage, nutraceutical, biotechnology, pharmaceutical, cosmetic, health and personal care industries in which the processing must take place in a hygienic or aseptic environment. Food processing equipment often needs to be cleaned between each lot of product processed through the equipment. However, the tanks, pumps, valves, and piping can be difficult to clean because the various components may be difficult to access and disassemble for cleaning Because of these cleaning difficulties, many food processing plants now use Clean-In-Place systems in which the tanks, pumps, valves, and piping of the food processing equipment remain physically assembled, and various cleaning, disinfecting, and rinsing solutions are circulated by the Clean-In-Place system, at high velocities, through the food processing equipment to affect the cleaning process.
During a CIP process, a cleaning fluid is run through the process line at high velocities in order to clean the process line. The flow rate for a CIP process is determined by the largest area present in the line, which then corresponds to the area with the least velocity. A minimum velocity for a CIP process can be set by the relevant industry standard, but generally, a minimum velocity of 5 ft/second is recommended in order to achieve effective cleaning results (see for example, guidelines for EHEDG (European Hygienic Engineering & Design Group)).
For CIP applications, it is desirable to use a flow meter system that is compact in size. The line sizes for the compact flow meters used for hygienic applications, including in CIP systems, necessarily must be smaller in order to be compatible with the compact flow meter and cases. Typically tubes can be welded to the manifold from the face of a manifold to allow for the tubes to be closer together in the case. In current hygienic flow meters having less than a 3 inch line size, the tubes are welded on the backside of the manifolds, which requires the tubes to be separated further to allow access for welding. This separation of tubes also leads to individual cases for each size tube. For example, when using 9 lines, three cases are employed with three line sizes each using the same case.
In hygienic applications, the lines used with the flow meters typically are of various sizes that are considered to be in the “hygienic range”. Arrangement of multiple lines having different sizes on the cases leads to manifold areas being excessively large when compared to the line sizes in which the flow meters are used, resulting in flow velocity that falls below the CIP required flow velocity of 5 ft/sec.
The embodiments described below overcome these and other problems and an advance in the art is achieved. The embodiments described below provide a hygienic manifold for a compact flowmeter that addresses the issue of increased area of the manifold and simultaneously maintains a compact tube design and cases for use in a CIP system.